Misjudgment of pre-stroke functional status contradicts beneficial outcomes after endovascular therapy for large vessel occlusion, Abstract Endovascular therapy (EVT) trials enrolled ischemic stroke patients with good pre-stroke functional status. However, this information needed for rapid decision-making is commonly lacking in clinical practice. We hypothesized that initial misjudgment of pre-stroke functional status attenuates clinical outcomes of EVT. Data were derived from our prospective registry of ischemic stroke patients undergoing EVT for anterior circulation large vessel occlusion (01/2016–12/2017). Considering all information accumulated during hospital course, pre-stroke modified Rankin scale (mRS) was independently re-assessed and compared with pre-EVT assessments. Misjudgment was defined as any difference in mRS categories between first- and second-look assessments. Multivariable model was built to adjust for confounding variables of unfavorable outcome (mRS 3–6) and death at 90 days. Overall, we studied 217 patients: median age 75 years (IQR 64–81), 54% women, median NIHSS 17 (12–20) points. Second-look assessment of pre-stroke mRS revealed 73 (34%) cases initially being misjudged by ≥ 1 category and 17 (8%) by ≥ 2 categories. None of the second-look mRS assessments resulted in a lower mRS category than initially rated. Patients whose pre-stroke mRS score was misjudged prior to EVT showed more frequently unfavorable outcome (62/73 [84.9%] vs. 94/144 [65.3%], p = 0.002) or were deceased (30/73 [41.1%] vs. 25/144 [17.4%], p < 0.001) at 90 days than patients with consistent mRS assessments. Moreover, unfavorable outcomes occurred in nearly all patients whose initial mRS was misjudged by ≥ 2 categories (mRS 3–6: 17/17 [100%]; death: 14/17 [82.4%]; p < 0.001). In conclusion, thorough pre-EVT assessment of pre-stroke functional status appears decisive for proper selection of EVT candidates.